An infrared nondestructive testing method and system for detecting defects of a wooden column of a wall of an ancient building

Abstract

The present application relates to a kind of infrared nondestructive testing methods and systems for detecting the defect condition of ancient building wall wood column.The infrared detection device of wall wood column is built, and clear infrared image is obtained at regular intervals;The infrared thermal image set obtained is perspective transformed, and corrected as the infrared image set under orthographic projection, and the infrared image noise is removed based on median filtering;Edge detection is carried out on its gray image using Canny operator, and the best threshold is obtained using adaptive iteration method, and further threshold highlight edge map is obtained, to determine the defect position and defect degree.The system detects the defect of wall wood column by active infrared nondestructive testing technology, overcomes the technical difficulties of effectively detecting the defect of wall wood column by current nondestructive testing means, and has the advantages of strong portability, simple operation, no need to contact and the like.Provides a new method and system for nondestructive testing of the defect condition of wall wood column, and has very important practical significance for nondestructive testing research of ancient building.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of non-destructive testing of wall wood columns, and particularly relates to an infrared non-destructive testing method and system for detecting defects of ancient building wall wood columns. BACKGROUND

[0002] Wood columns are one of the key load-bearing components of ancient wooden buildings, supporting all the loads on the top of the ancient buildings. According to the position relationship between the wood columns and the wall, the wood columns can be divided into wall wood columns and independent wood columns. Due to the effects of environmental moisture and insect damage, the wall wood columns will first develop decay defects from the root, affecting their mechanical properties, and further posing a safety hazard to the ancient buildings. Therefore, to effectively protect the ancient wooden buildings, it is crucial to regularly detect the defects of the wall wood columns.

[0003] According to the ancient building wood structure detection standard (T / CECS 714-2020) and the ancient building structure safety appraisal technical specification first part: wood structure (DB11 / T1190.1-2015), there are two methods for detecting defects of ancient building wall wood columns, the first being the micro-drill resistance instrument method, and the second being the stress wave method. However, these two methods cannot effectively detect decay defects in the embedded part of the wood column and the wall, especially for the wall-in hidden column that is completely wrapped by the wall. When there is a temperature difference on both sides of the wall, the defect and the non-defect area of the wood column produce different infrared radiation. By detecting the temperature changes on the surface of the wall using an infrared thermal imager, the internal defects can be explored.

[0004] The infrared thermal imager can measure all temperatures in a large range, has fast detection speed, accurate positioning, and visualized graphics, and can be used to obtain temperature information of defects. However, different shooting angles will form deviated temperature data, and due to the working principle, a large amount of random noise is easily mixed. Therefore, when obtaining infrared images, there is a problem of incomplete expression of image information, and a large amount of noise affects the image quality, which brings difficulties to defect detection, hinders the acquisition of defect positions, and further affects the judgment of defect degrees. SUMMARY

[0005] In view of the problems existing in the prior art, the present application provides an infrared non-destructive testing method and system for detecting defects of ancient building wall wood columns, which can realize non-secondary damage defect detection of wall wood columns with different damage degrees using infrared thermal imaging technology, and use software algorithms to compensate for the shortcomings of hardware devices to obtain complete infrared image sequences with rich details and clear expression in a unified view, and obtain defect information.

[0006] In a first aspect, the present application provides an infrared non-destructive testing method for detecting defects of ancient building wall wood columns, characterized in that the method comprises:

[0007] (I) Build a wall body wood column infrared detection device, get clear wall body wood column defect infrared image in time, expand into heat map sequence in time dimension;

[0008] (II) Perspective transformation is carried out on the obtained infrared heat map set, and the infrared image set under orthographic projection is corrected, and the infrared image noise is removed based on median filtering;

[0009] (III) The Canny operator is used for edge detection of the gray image, and the best threshold is obtained by using the adaptive iteration method, and the threshold highlight edge map is further obtained, so that the defect position and defect degree are determined.

[0010] By using the above implementation mode, the technical difficulties of effectively detecting the wall body wood column defect by the current nondestructive testing method of wood can be overcome; the software algorithm makes up for the deficiency of the hardware device, obtains a complete infrared image sequence with rich details and clear expression under a unified view, and obtains defect information by edge extraction of the wall defect position. A new method and system are provided for nondestructive testing of wall body wood column defect condition, which has very important practical significance for nondestructive testing research of ancient buildings.

[0011] In combination with the first aspect, in a first possible implementation mode of the first aspect, the clear wall body wood column defect infrared image set is obtained by the built wall body wood column defect infrared detection device, and the wall body wood column defect infrared detection device is flexible to build and accurate to detect. The device mainly consists of a computer (1), an infrared thermal imager (2), a wall body wood column (3), and a vibration source assembly (4). The vibration source includes a self-heating industrial electric heating device (4.1), a heat preservation rear cover (4.2), a support truss (4.3), and an aluminum plate (4.4).

[0012] The clear infrared image set is obtained in the following manner: there are wood columns with different defect degrees in the ancient building wall body, based on the built wall body wood column defect infrared detection device, the wall body wood column with defects is continuously subjected to heat conduction, and the infrared thermal imager is used to take pictures at regular time intervals, and the heat map sequence is expanded in time dimension.

[0013] In combination with the first aspect, in a second possible implementation mode of the first aspect, the infrared thermal image under orthographic projection is obtained in the following manner: perspective transformation is carried out on the clear and complete infrared image set, and the infrared image set under orthographic projection is corrected to obtain accurate image information.

[0014] The first image of the heat map sequence is selected as a reference image, perspective transformation is carried out on four right-angle points of the wall, the image is projected to a new view plane, and the heat map sequence under orthographic view is obtained after batch operation of the remaining images.

[0015] With reference to the first aspect, in a third possible implementation manner of the first aspect, the thermal image sequence under the front view is mixed with a large amount of random noise and image information, removal of the random noise uses a median filtering method, and the method comprises the following steps:

[0016] The thermal image sequence under the front view is preprocessed to be grayed, pixels in a local region are sorted according to a gray level, a median value of the gray level in the region is taken as a gray value of a current pixel, and a gray image sequence after median filtering is obtained.

[0017] With reference to the third possible implementation manner of the first aspect, in a fourth possible implementation manner of the first aspect, a Canny operator is used to perform edge detection on the gray image to obtain edge details of the best algorithm and the wall wood column defect condition enhanced image, a best threshold value is obtained by using an adaptive iteration method, and a threshold highlighted edge map is further obtained, and an area contained by an edge contour is the defect area.

[0018] The second aspect provides an infrared nondestructive detection system for detecting a wall wood column defect condition of an ancient building, and the system comprises: an image acquisition module configured to read a clear infrared thermal image obtained by an infrared thermal image acquisition component; an image processing module configured to perform perspective transformation on the obtained infrared thermal image, correct the infrared thermal image to an infrared thermal image under a front view, and perform median filtering on the infrared thermal image to eliminate noise and improve image quality; and a defect analysis module configured to perform edge detection on a gray image of the infrared thermal image by using a Canny operator, obtain a best threshold value by using an adaptive iteration method, and further obtain a threshold highlighted edge map, so that discontinuous parts and contrast degrees of a wall surface temperature are directly shown, and a defect position and a defect degree are determined.

[0019] With reference to the second aspect, in a first possible implementation manner of the second aspect, the image processing module comprises:

[0020] A first processing unit is configured to perform perspective transformation on the clear and complete infrared image set, correct the infrared image set to an infrared image set under a front view to obtain accurate image information. A first image of the thermal image sequence is selected as a reference image, perspective transformation is performed on four right-angle points of the wall to project the image to a new view plane, and the remaining images are batch-operated to obtain a thermal image sequence under the front view.

[0021] A second processing unit is configured to pre-process the thermal image sequence under the front view to gray the thermal image sequence, sort pixels in a local region according to a gray level, take a median value of the gray level in the region as a gray value of a current pixel, and obtain a gray image sequence after median filtering.

[0022] In a third aspect, the present application provides a computer program product, which comprises a computer program stored on a non-transitory computer-readable storage medium, the computer program comprising program instructions which, when executed by a computer, enable the computer to implement the steps of any of the above-mentioned infrared image processing methods for detecting defects of a wooden column of a wall of a historic building. DETAILED DESCRIPTION

[0023] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described clearly and completely below with reference to the drawings in the present application. Obviously, the described examples are part of, but not all of the examples of the present application. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0024] The infrared non-destructive testing method and system for detecting defects of a wooden column of a wall of a historic building of the present application will be described below. Figures 1-3

[0025] Figure 1 is a flowchart of the infrared non-destructive testing method for detecting defects of a wooden column of a wall of a historic building provided by the present application, as shown in Figure 1 , the method comprises the following steps.

[0026] S101, a wall body wooden column infrared detection device is built to obtain clear infrared images of the defect conditions of the wall body wooden column in time, and the infrared images are expanded into a thermal image sequence in the time dimension, as shown in Figure 2 .

[0027] The clear infrared image set of the defect conditions of the wall body wooden column is obtained by the self-built wall body wooden column defect condition infrared detection device, and the wall body wooden column infrared detection device is composed of an image analysis computer (1), an infrared thermal imager (2), a defect wooden column (3) and a vibration source assembly (4).

[0028] ​The vibration source assembly (4) is close to the actual wall side, which comprises a self-heating industrial electric heating device (4.1), a heat preservation rear cover (4.2), a support truss (4.3), and an aluminum plate (4.4). The self-heating industrial electric heating device (4.1) can achieve temperature control of 0-100℃, the heat preservation rear cover (4.2) is connected by angle steel and is in a hollow and coverless box state, and is filled with four layers of heat insulation materials with equal and uniform thickness. The support truss (4.3) uses a triangular structure to ensure the close fit of the vibration source and the wall, and also plays a fixing and supporting role. The aluminum plate (4.4) is connected by bolts and nuts at the opening of the heat preservation rear cover (4.2). The self-heating industrial electric heating device (4.1) is fixed on one side of the aluminum plate (4.4) by a magnet. The infrared thermal imager (2) is fixed on an adjustable height and angle tripod and placed at a certain horizontal distance from the measured wall wood column. The computer (1) is used for post-processing of the collected on-site thermal images (1.1).

[0029] When using the wall wood column infrared detection device to collect the infrared image set of the wall wood column defect condition, first, the assembly of the device is completed, the support truss (4.3) uses a triangular structure to ensure the vertical stable placement of the vibration source assembly (4) and the close fit with the wall, and the infrared thermal imager (2) is adjusted to a position where it can shoot complete wall wood column infrared thermal images. Second, the self-heating industrial electric heating device (4.1) is connected to the power supply for constant heat conduction, so that the wall and the defective wood column (3.1) are continuously and uniformly heated, and the aluminum plate (4.4) is uniformly laid with nine temperature sensors as a heat sensing device on the wall side, which can monitor the temperature change in real time and record the temperature change process time. After the wall heating surface is uniformly heated, the infrared thermal imager (2) placed at a certain distance continuously shoots the wall wood column after the vibration source is heated at the same interval. The gaps between the plate blocks of the heat preservation rear cover (4.2) are filled with heat insulation materials, which can effectively block heat loss. Then, the power supply of the self-heating industrial electric heating device (4.1) is disconnected, and the vibration source heating is stopped. The infrared thermal imager (2) continues to shoot the wall wood column after the self-heating industrial electric heating device (4.1) is heated until the temperature of the wall side cools down to room temperature, and clear and effective thermal image sets can be obtained. Finally, a series of thermal image sets are transmitted to the computer for subsequent processing.

[0030] S102, perspective transformation is performed on the obtained infrared thermal image set, and the infrared image set under orthographic projection is corrected, and median filter is used to remove infrared image noise.

[0031] The clear and complete infrared image set is perspective transformed and corrected to an infrared image set under orthographic projection to obtain accurate image information. The first image of the thermal image sequence is selected as a reference image, four right-angle points of the wall are selected for perspective transformation, and the thermal image sequence under orthographic projection is obtained after batch operation of the remaining images.

[0032] In S103, the Canny operator is used to perform edge detection on the gray image, and the adaptive iteration method is used to obtain the best threshold value, and a threshold highlighted edge map is further obtained to determine the defect position and defect degree.

[0033] The Canny operator is used to perform edge detection on the gray image, the edge details of the wall body wooden column defect condition enhancement image are obtained, and the adaptive iteration method is used to obtain the best threshold value, and a threshold highlighted edge map is further obtained, and the area contained by the edge contour is the defect area, and the defect position and defect degree can be determined through edge detection.

[0034] Corresponding to the infrared nondestructive detection method for detecting the defect condition of the wall body wooden column of the ancient building provided in the above embodiment, the present application further provides an example of an infrared nondestructive detection system for detecting the defect condition of the wall body wooden column of the ancient building. Figure 3 is a structural schematic diagram of an infrared nondestructive detection system for detecting the defect condition of the wall body wooden column of the ancient building provided by the present application, as Figure 3 shown, the wall body wooden column defect nondestructive detection system 20 comprises an image acquisition module 201, an image processing module 202 and a defect analysis module 203. The image acquisition module is used to read the clear infrared thermal image obtained by the infrared thermal image acquisition assembly; the image processing module is used to perform perspective transformation on the obtained infrared thermal image, correct the infrared thermal image under orthographic projection, and perform median filtering thereon to eliminate noise and improve image quality; the defect analysis module uses the Canny operator to perform edge detection on the gray image, and uses the adaptive iteration method to obtain the best threshold value, and further obtains a threshold highlighted edge map to determine the defect position and defect degree.

[0035] Further, the image processing module 202 comprises a first processing unit and a second processing unit.

[0036] The first processing unit is used for perspective transformation of the clear and complete infrared image set, and correction of the infrared image set under orthographic projection to obtain accurate image information.

[0037] The second processing unit is used for pre-processing of the thermal image sequence under orthographic projection to gray scale, sorting of pixels in a local area according to gray scale levels, taking a median value of the gray scale in the field as a gray scale value of a current pixel, and obtaining a median filtered gray scale image sequence.

[0038] The present application also provides a computer program product, which comprises a computer program stored on a non-transitory computer readable storage medium, and the computer program comprises program instructions, when the program instructions are executed by a computer, the computer can execute the infrared image processing method for defect conditions of a wooden column of a historic building wall provided by the above-mentioned methods, and the infrared image processing method comprises the following steps: reading an infrared detection image set acquired by a wall wooden column defect condition infrared acquisition device, and expanding the infrared detection image set into a thermal image sequence in a time dimension; performing perspective transformation on the obtained infrared thermal image set, correcting the infrared thermal image set under orthographic projection, and removing infrared image noise based on median filtering; performing edge detection on a gray scale image thereof using a Canny operator, and obtaining a best threshold value using an adaptive iterative method, and further obtaining a threshold highlighted edge map to determine a defect position and a defect degree.

[0039] In another aspect, the present application also provides a non-transitory computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the infrared image processing method for defect conditions of a wooden column of a historic building wall provided by the above-mentioned examples, and the infrared image processing method comprises the following steps: reading an infrared detection image set acquired by a wall wooden column defect condition infrared acquisition device, and expanding the infrared detection image set into a thermal image sequence in a time dimension; performing perspective transformation on the obtained infrared thermal image set, correcting the infrared thermal image set under orthographic projection, and removing infrared image noise based on median filtering; performing edge detection on a gray scale image thereof using a Canny operator, and obtaining a best threshold value using an adaptive iterative method, and further obtaining a threshold highlighted edge map to determine a defect position and a defect degree.

[0040] The system embodiments described above are only schematic, wherein the units illustrated as separate components may or may not be physically separate, and the components illustrated as units may or may not be physical units, that is, they may be located in one place or distributed on a plurality of network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the present embodiment. Those skilled in the art can understand and implement without creative labor.

[0041] Through the description of the above embodiments, those skilled in the art can clearly understand that the embodiments can be realized by means of software on the necessary general hardware platform, and of course can also be realized by hardware. Based on such understanding, the above technical solutions can be embodied in the form of a software product in essence or in the form of a part of the prior art, and the computer software product can be stored in a computer readable storage medium, such as a ROM / RAM, a magnetic disk, an optical disk, etc., and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the method described in each embodiment or some parts of the embodiment.

[0042] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

[0043] The beneficial effects of the present application are:

[0044] The present application detects the defects of the wall body wooden column through the active infrared nondestructive detection device, compared with the current micro drill resistance method which can only obtain limited defect information of the measured path each time, the stress wave method has a large destructive behavior on the wall building, the infrared thermal imaging technology can quickly obtain large area temperature field information to judge the damage position and the damaged degree of the detected wooden column, and overcomes the technical difficulties of the current nondestructive detection means for effectively detecting the defects of the wall body wooden column.

[0045] Different shooting angles of the infrared thermal imager will form deviated temperature data, and a large amount of random noise is easily mixed due to the working principle itself. Therefore, the present application solves the problem that the image information expression is not complete when the infrared image is acquired, and a large amount of noise affects the image quality. The software algorithm makes up for the deficiency of the hardware device, acquires a complete infrared image sequence with rich details and clear expression under a unified view, and obtains the defect position and the defect degree through edge extraction of the wall defect part. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is a flowchart of the infrared nondestructive detection method for detecting the defect condition of the wall body wooden column of the ancient building provided by the present application;

[0047] Figure 2 is a schematic view of the nondestructive detection device for the defect condition of the wall body wooden column provided by the present application;

[0048] Figure 3It is structural schematic view of infrared nondestructive testing system for detecting defect condition of ancient building wall wood column provided by the application.

Claims

1. An infrared non-destructive testing method for detecting defects of a wooden column of a wall of an ancient building, characterized in that, The method comprises: (I) building a wall wood column infrared detection device, obtaining clear wall wood column defect condition infrared images in time, and unfolding into a thermal image sequence in time dimension; (II) performing perspective transformation on the obtained infrared thermal image set, correcting the infrared image set under orthographic projection, and removing infrared image noise based on median filtering; (III) using a Canny operator to perform edge detection on the gray image, and using an adaptive iterative method to obtain the best threshold value, and further obtaining a threshold highlighted edge map to determine the defect position and defect degree; The wall wood column defect infrared detection device is flexible to build and accurate to detect, mainly comprising a computer (1), an infrared thermal imager (2), a wall wood column (3), and a vibration source assembly (4), wherein the vibration source comprises a self-heating industrial electric heating device (4.1), a heat preservation rear cover (4.2), a support truss (4.3), and an aluminum plate (4.4).

2. The method of claim 1, wherein, The clear and complete infrared image set is subjected to perspective transformation and corrected into an infrared image set under orthographic projection to obtain accurate image information; the first image of the thermal image sequence is selected as a reference image, and four right-angle points of the wall are selected for perspective transformation, and the remaining images are batch-operated to obtain a thermal image sequence under orthographic view.

3. The method of claim 2, wherein, The thermal image sequence under orthographic view contains a large amount of random noise and image information, and the random noise is removed by using a median filtering method, which comprises: pre-processing the thermal image sequence under orthographic view to gray it, sorting the pixels in a local area according to the gray level, taking the median value of the gray level in the field as the gray value of the current pixel, and obtaining a gray image sequence after median filtering.

4. The method of claim 1, wherein, The Canny operator is used to perform edge detection on the gray image to obtain the edge details of the wall wood column defect condition enhancement image, and the adaptive iterative method is used to obtain the best threshold value, and further obtain a threshold highlighted edge map, and the area contained by the edge contour is the defect area.

5. An infrared nondestructive testing system for detecting the defect condition of a wall wood column of an ancient building, which adopts the method of claim 1, characterized in that the system comprises: an image acquisition module for reading clear infrared thermal images obtained by an infrared thermal image acquisition assembly; an image processing module for performing perspective transformation on the obtained infrared thermal image, correcting the infrared thermal image under orthographic projection, and performing median filtering to eliminate noise and improve image quality; a defect analysis module for using a Canny operator to perform edge detection on the gray image, and using an adaptive iterative method to obtain the best threshold value, and further obtaining a threshold highlighted edge map to determine the defect position and defect degree.

6. The system of claim 5, wherein, The image processing module comprises: a first processing unit for perspective transformation of the clear and complete infrared image set, correction of the infrared image set under orthographic projection to obtain accurate image information, selection of the first image of the thermal image sequence as a reference image, selection of four right-angle points of the wall for perspective transformation, projection of the image to a new view plane, batch operation of the remaining images to obtain a thermal image sequence under orthographic view, The second processing unit pre-processes the thermal image sequence under the front view, grays the thermal image sequence, sorts the pixels in the local region according to the gray scale, takes the median value of the gray scale in the region as the gray scale value of the current pixel, and obtains a median filtered gray scale image sequence.

7. Provide a computer program product, the computer program product comprises a computer program stored on a non-transitory computer readable storage medium, the computer program comprises program instructions, when the program instructions are executed by a computer, the computer can realize the steps of the infrared nondestructive testing method for detecting the defect condition of the wooden column of the ancient building wall as claimed in any one of claims 1 to 5.

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